In geotechnical engineering, man made composite materials are used in place of soil, clay, rock and the like to provide solutions to geotechnical engineering problems. Typical composite materials used in this field comprise two or more components such as textile sheets in combination with a grid, net or core. Typical applications for composite materials are provision of drainage and/or provision of moisture barrier around structures.
FIG. 1 shows a side sectional view of a known composite material 1 in use. The composite material 1 is supplied in sheets made up of drainage strips 10 positioned between textile layers 12. The textile layers 12 are permeable to water, whereas the drainage strips channel water along their length. In use the textile layers 12 are in contact with moist soil allowing water to pass into the drainage strips to be carried away from the soil. However, a problem arises when separate sheets of the composite material 1 are used to build up a drainage system over a large area. To enable efficient drainage, ends of the drainage strips forming a drainage outlet from a first material sheet must be carefully aligned with the ends of drainage strips forming a drainage inlet to a second material sheet. This may not be straightforward in cases where the sheets extend over large distances, are subject to crumpling between drainage strips and the drainage strips themselves are relatively narrow. Furthermore, separate drainage strips can not easily cooperate with one another to distribute drainage flow to other strips should any strip or strips become blocked.
Example embodiments of the present invention aim to address at least one disadvantage of the prior art, whether identified herein or otherwise.